Analysis And Study For Grid-connected Inverter Control Strategy Based On Adaptive Fuzzy Control

Recently, power energy feedback system has becomed a hotspot. Grid-connected inverter is a device that realizes power energy feedback to grid. To get high PF and low harmonic, researching inverter's control strategy is very meaningful.Establishing mathematic model is the basis of researcing inverter's control system. However, grid-connected inverter is a no-linear system and its parameters are changing by time. So it is difficult to establish a precise model. Thus, in this thesis, the model and a two-closed-loop control strategy of stand-alone inverter is presented first. Then the design method of PI controller's parameters is analysised. On the other hand, this thesis analyzes LC filter and designs parameters for it. By simulating in MATLAB, this thesis validates that the control effect is pretty good for stand-alone inverter.On the basis of researching stand-alone inverter, this thesis focuses on grid-connnected inverter's control strategy and suitable strategies in different working situations. There are three types of inverters according to their different filter topologies: L filter, LC filter and LCL filter. A single-phase inverter is taken as an example. This thesis analyzes control strategy for different topology, including single current loop control and double current loop control. Then this thesis focuses on LCL filter's capacity and design method, and gives out its advantage. By analysis of simulating outcome, this thesis proposes suitable control strategy and working situations for the three kinds of filters.To improve gird-connected inverter's performance under the condition of comparatively large external perturb, in this thesis two kinds of control strategies based on fuzzy control applied to grid-connected inverter system are proposed: scale factor adaptive fuzzy control and PI parameter adaptive fuzzy control. This thesis designs this control strategy for a single-phase inverter and does simulation in MATLAB. Then it is validated that adaptive fuzzy control can improve grid-connected inverter's performance and robust. It is adapted to grid-connected inverter control system which suffered from a relatively great disturbs from outside.At last, on the basis of researching single-phase grid-connected inverter, three- phase inverter's control strategy is discussed and the control strategy of adaptive fuzzy control is designed. By simulating, it is validated that the model is correct and the control strategy is good.